RU2419509C2 - Method and device for continuous casting of steel preliminary sections, particularly, h-sections - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to metallurgy. Proposed device comprises crystalliser consisting of two shelf sections 2 and 3 and one transverse section 4, secondary cooling device wiring and electromagnetic mixer with six or more coils connected to phases of three-phase current source. Proposed method comprises feeding liquid steel in crystalliser 1 and acting on blank liquid core by electromagnetic field induced by mixer coils 19. Three-phase AC is fed to said coils to generate travelling fields with their components directed across blank motion. Fields with unidirectional- or opposite-direction-revolving components are generated in said shelf sections 2 and 3 and/or fields with linear- or opposite-direction components are generated in transverse section. Travelling fields are generated at different heights over the blank. ^ EFFECT: controlled miffing conditions and temperature and reduced amount of surface defects. ^ 14 cl, 15 dwg

Description

The invention relates to a method for the continuous casting of steel profiles, in particular I-beam draft profiles according to the restrictive part of paragraph 1 of the claims, as well as a device for implementing this method.

Rough steel profiles are semi-finished products for the production of steel beams with I, H, U and Z-shaped cross-section, as well as special sheet pile profiles. A method for continuously casting such profiles is disclosed, for example, in EP-B-1419021. Continuous casting of rough profiles was introduced in industry in the 70s and has been gaining more recently in the presence of a general tendency towards the so-called casting with final dimensions.

Draft profiles are mostly cast in the form of an I-beam, with liquid steel being introduced, essentially, vertically into the so-called “dog-bone” mold through passage, the cross-section of the molding space of which consists of two shelf sections and one wall section. From the mold, the preform with a liquid core is fed to a guide line for the preform with a secondary cooling device.

In contrast to the continuous casting of classic long products with a rectangular or circular cross-section, the continuous casting of I-beams rough profiles has several problems, especially when it comes to rough profiles with a relatively thin wall, and if high-strength products are cast from special steel grades (CaSi- or Al - Reduced, microalloyed steel with V, Nb, etc.), or at high-speed casting. For reasons of location, as well as for economic reasons, molten steel is poured into the mold through only one pouring cup, often asymmetrically located at the interface between the wall (transverse section) and one of the shelves. As a result of this, it is especially difficult to uniformly and without disturbing turbulence fill the complex cavity of the mold and create favorable conditions for initial solidification to avoid surface defects (gas bubbles, microchannels). It is also difficult to achieve a symmetric flow inside the workpiece crust and, therefore, a symmetric temperature distribution, which ultimately leads to a homogeneous solidification structure. It is also problematic for a thin transverse section to avoid freezing (arching) during hardening and, as a result, axial porosity and / or shrinkage shells.

From JP 08294746 A, molds are known for the continuous casting of I-sections of rough profiles. Liquid steel through 2 immersion glasses is poured into both sections of the shelves. To avoid surface defects on the draft profile, it is proposed to arrange a pair of permanent poles of pole magnets outside the molding space both on both external sides of the shelf sections and on both sides of the transverse section with S or N poles. Due to the constant magnetic field just below the neck of both immersion nozzles, steel flow slows down and spreads horizontally to the walls of the mold and along them back to the bathtub mirror. Under the influence of a constant magnetic field with poles N and S, a braking effect is achieved for the resulting vertical flow from immersion nozzles and an uncontrolled deviation of the flux from the vertical. Controlled, controlled traveling fields and, accordingly, flows in the liquid core to create controlled flow conditions and the temperature of the rough profile are not used at this level of technology.

The basis of the present invention is to propose a method of the above type, as well as a device for implementing this method, with which steel profiles, which have two shelves and one transverse section, can be manufactured with improved quality, even if draft profiles have a relatively thin transverse section and / or cast from special steels. In the future, it would be possible to choose, depending on the size or quality of the steel of the rough profiles, symmetric or asymmetric pouring of steel into the mold with one or two open or closed glasses.

This problem is solved by the method according to paragraph 1, as well as by means of a device with the features of claim 8.

Advantageous variants of the method according to the invention, as well as the corresponding device are presented in the respective dependent clauses.

Due to the fact that according to the invention, the liquid core of the rough profile is brought into the mixing movement across the continuous casting direction by the forces of electromagnetic induction in the area of the shelf sections and / or the wall section, and due to the mixing movement, the liquid steel in the core of the rough profile between the shelf and wall sections is mixed, it is possible purposefully exert an active influence on the flow conditions and temperature in liquid steel inside the mold of the rough profile and thus azom achieve the following effects:

- stabilization of the zone of the bath mirror by suppressing turbulence even with changing process parameters, such as casting speed, the position of the metal mirror (in order to avoid non-metallic inclusions such as gas bubbles on the surface of the cast billet);

- favorable, controlled flow conditions with targeted mixing of liquid steel between both regions of the shelves in the mold space through the region of the thin transverse section, as well as during asymmetric casting, thereby achieving the formation of a uniformly thick workpiece crust with a favorable solidification structure to avoid shrinkage of shells and / or porosity kernels;

- avoiding the formation of jumpers (freezing) during solidification, despite the narrow proportions in the wall of the cross section of the molding space.

Additionally, with varying grades of steel or different sizes of rough profiles, various combinations of traveling fields in the areas of shelves and / or transverse sections can be selected with the same mixing means. At the same time, it is possible, when the filling system is changed without constructive changes in the mixing means (stirrer), to generate traveling fields with completely different guide components in the areas of the shelves and / or the transverse section. The invention is further illustrated by means of the drawings, in which are schematically represented:

Figure 1 shows a cross section of a mold in a first embodiment of an electromagnetic mixer.

Figure 2 presents a cross section of a mold with a second embodiment of an electromagnetic mixer.

Figure 3-6 shows a third embodiment of an electromagnetic stirrer for a mold with various connections of the pole pieces.

Figures 7 and 8 show a mold with two mixers with different connection of the pole pieces.

Figure 9 presents the mold with two mixers in side view.

10 shows a croister with two mixers in another embodiment.

11 and 12 show a mold in another embodiment with various connection of the pole pieces.

On Fig presents a side view of the mixer shown in Fig.10.

On Fig presents another embodiment of a mold with an electromagnetic stirrer.

On Fig presents an electrical diagram for the mixer shown in Fig.

Figure 1 shows a schematic illustration of the mold 1, respectively, its horizontal cross section, which is composed of two sections 2, 3 shelves and the transverse section 4. The mold 1 is designed for continuous casting of I-sections. Liquid steel flows substantially vertically into this passage through the mold, where a workpiece crust is formed and from which the workpiece in the form of a draft profile with a liquid core is fed into the guide wiring with a secondary cooling unit.

According to the invention, the liquid core of the rough profile, preferably in the area of the mold 1 or directly at the outlet of the mold 1, is mixed by means of an electromagnetic stirrer 10, powered by a three-phase current, under the influence of electromagnetic induction across the direction of continuous casting, and thereby the liquid steel is distributed in the liquid core blank draft profiles between sections 2, 3 of shelves and transverse section 4.

The mixer 10 shown in FIG. 1 is an annular, continuous mold yoke 11 at a known height 1 with six magnetic poles in the form of pole pieces 12 to 17, each pole piece being surrounded by one electromagnetic coil 19. The pole pieces 12 to 17 are distributed unevenly around the yoke 11 in such a way that one pole tip 12, 13 is oriented to sections 2, 3 of the shelves and two pole pieces 14, 15 and 16, 17 are directed to both sides of the transverse section 4. The mixer 10, in In this embodiment, the rotary mixer operates on the principle of a 6-pole asynchronous motor, in which a traveling field can be generated using a three-phase current. In this case, it is important to observe the correct connection of the poles, so that a linear or rotational field and, accordingly, linear or rotating flows arise.

In the embodiment shown in FIG. 2, the mold 1 is again surrounded on a known and predominantly height-adjustable section by an electromagnetic stirrer 20 with an annular one-piece yoke, along the perimeter of which again six pole pieces 22 to 27 are unevenly located, with the difference that all six pole pieces 22 to 27 are oriented essentially to linear flows in the transverse section 4.

In FIG. 3 to 6, an electromagnetic mixer 30 is installed on the mold, which is a female mold 1, made integral in the form of a yoke 31 in the form of a rectangular frame, and three pole pieces 34, 35, 36 and 37, 38, 39 are distributed along the mold width on its longitudinal sides and in the narrow part it is provided for one middle pole piece 32, 33 frontally located to sections 2, 3 of the shelves. As will be presented below, the mixer 30 can operate both in rotational and in linear mode, depending on Turning poles, ie from which pole pieces and in what order in phase (phases are designated U, V, W; U ', V', W ') are connected to the current. In FIG. From 3 to 6, four different applications are proposed, in which, depending on the circumstances, six of the total number of eight pole pieces are supplied with current.

In the connection of the poles shown in FIG. 3, the middle pole pieces 32, 33 in the region of the shelf sections are turned off and the pole pieces 34, 35, 36 on the longitudinal side of the yoke 31 are out of phase compared with the pole pieces 37, 38, 39 on the other longitudinal side, due to which there is a linear counter flow in the transverse section 4 (2 × 3-pole linear, counterflow). This connection of the poles is applicable mainly with symmetrically located jellies 45, 46 in sections 2, 3 of the shelves.

Figure 4 shows the connection also for linear mode (the middle pole pieces 32, 33 in the shelf section are turned off), with a sequence of phases U, V, W on both longitudinal sides, so that uniform flow (2 × 3- pole drive, synchronous). This connection of the poles is applicable mainly with asymmetrically located filler nozzle 47 in section 2 or 3 of the shelves.

In the connection shown in FIG. 5, current is supplied to the middle pole pieces 32, 33 in the region of the shelf sections, however, the middle of the three pole pieces 34, 35, 36; 37, 38, 39, which are located on both longitudinal sides, are disconnected (pole pieces 35, 38 are de-energized). Thus, a rotational field (2 × 3-pole rotary drive) arises in the sections of the shelves. With the indicated phase distribution along the pole pieces 37, 32, 34 and 36, 33, 39, the directions of rotation of the rotation fields in both sections 2, 3 of the shelves are the same, and there is also a flow in the transverse section 4, which is of course less than with the linear drive presented figure 3. This connection of the poles is applicable mainly with a symmetrically located jellied glass gate 48 in the wall section 4.

When connecting the pole pieces 37, 32, 34 and 36, 33, 39, as shown in Fig.6, it is possible with the mixer 30 to produce also a rotational field with the opposite direction of rotation in sections 2, 3 of the shelves. This connection of the poles is applicable mainly with two symmetrically located pouring glasses 45, 46 in sections 2, 3 of the shelves.

Figures 7 and 8 show variants in which two electromagnetic mixers 40, 40 'and, respectively, two yokes 41, 41', each of which have three pole pieces 42, 43, 44, are located along the perimeter of the mold; 42 ', 43', 44 ', and each yoke 41, 41' has one middle pole piece 42, 42 ', frontally directed to the respective sections 2, 3 of the shelves, and two pole pieces 43, 44; 43 ', 44' on both sides of sections 2, 3 of the shelves. With both mixers 40, 40 'it is again possible to create a 2 × 3-pole rotational mode, respectively a rotational field in sections 2, 3 of the shelves, which again have the same (Fig. 7) or opposite (Fig. 8) direction of rotation. Position 48 means a symmetrically located pouring glass.

With two mixers 40, 40 ′ located in wide parts of the crystallizer 1 and, respectively, with two yokes 41, 41 ', one can achieve almost the same action as with one mixer 30 with an integral yoke 31 connected according to FIGS. 5 or 6. In addition, this solution provides an additional advantage. The electromagnetic mixer can be made in the form of two independent mixers or half-mixers, which are relatively easy to mount outside the mold 1. Through the free sector provides additional structural space. Last but not least, this solution also allows you to place both mixers 40, 40 'on opposite sides at different heights, as shown in Fig.9, and the opposite and / or height-shifted arrangement of mixers 40, 40' can be implemented as needed. Position 49 shows an asymmetric filling cup.

Similar advantages are also offered by the solutions shown in FIG. from 10 to 12, in which along the perimeter of the mold 1 are again two electromagnetic mixers 50, 50 '(in Figs. 10 to 13) and 60, 60' (in Figs. 11 and 12), respectively, which however have separate from another yoke 51, 51 'and, respectively, 61, 61', not in the width direction, but in the thickness direction of the mold 1. Each yoke is equipped with three pole tips 52, 53, 54; 52 ', 53', 54 'and, respectively, 62, 63, 64; 62 ', 63', 64 '.

In the embodiment of the invention shown in FIG. 10, three pole pieces 52, 53, 54; 52 ', 53', 54 'are distributed over the entire width of the rough profile, and two of them (pole pieces 52, 54; 52', 54 ') located on the sides of sections 2, 3 of the shelves, and the middle pole piece 53, 53 'raised to the transverse section 4.

In the embodiments of the invention shown in FIGS. 11 and 12, all three pole pieces 62, 63, 64; 62 ', 63', 64 'of the respective mixers 60, 60' are distributed only above the wall and are directed towards the transverse section 4. Positions 45, 46 show two symmetrical filling cups.

The mixers 50, 50 'and, respectively, 60, 60' operate as linear, and in the transverse section 4 can generate unidirectional flows (Fig.10 or 11) or unidirectional flows (Fig.12). The setting is carried out depending on the casting parameters and / or the product.

FIG. 14 shows an electromagnetic stirrer 70 with an 8-pole structure, structurally similar to the stirrer 30 shown in FIG. 3 to 6 (with a yoke formed by a rectangular frame, the longitudinal sides of which are equipped with pole pieces 74, 75, 76, 77, 78, 79 located three times across the mold and the narrow part has one mid-pole piece 72, 73, frontally directed to sections 2, 3 shelves). Of course, in this embodiment, one does not choose between linear or rotational mode by turning off two of the eight poles, however, linear fields are generated in the transverse section 4 at the same time using a 1 × 6-pole linear stirrer (pole terminals 74, 75, 76, 77, 78, 79) and rotation fields in sections 2, 3 of shelves when using 2 × 3-pole rotary mixers (pole tips 74, 72, 77 and 76, 73, 79).

On Fig presents the electrical circuit of the mixer 70 with its 8-pole structure and, accordingly, with an 8-pole system, in which linear fields are simultaneously produced using a 1 × 6-pole linear mixer and rotational fields when using 2 × 3-pole rotary mixers. Such an electromagnetic mixer 70 is powered from a network, for example, 50 Hz alternating current through lines 81, 82, and these lines lead to a single frequency converter 83, 84 as necessary. This frequency converter 83, 84 is connected to the controller 85, and the individual phases are adjusted them to a known frequency.

The controller 85 has the task of adjusting the frequencies of both transducers one after the other in order to synchronize on the one hand the mixing movements occurring in the wall and in the transition region to both sections of the shelves. In addition, it should prevent the occurrence of beats with slight frequency differences in both mixers. The runout would lead to the fact that over time, one or the other pole would simultaneously be energized, which would result in a very uneven load on the network.

Separate phases U, V, W of one converter 84 and, correspondingly, phases U1, V1, W1 of another converter 83 to the coils wound around the pole pieces 74, 75, 76, 77, 78 are drawn from these frequency converters 83, 84. The phases U, V, W lead to the coils 77 ', 78', 79 'on the pole pieces 77, 78, 79 in the transverse section and then to the coils 76', 75 ', 74' of the pole pieces 76, 75 symmetrically positioned relative to them , 74, and the connecting wires from the coils 77 ', 79' are drawn crosswise to the coils 76 ', 74' (included in the series).

Outgoing wires from these coils are connected to point 87 of the star. It is similarly provided with phases U1, V1, W1, which, however, is not explained in detail. In the linear mode, the phase W1 is supplied to the coil 72 'and then to the opposite coil 73' and to the point 88 of the star.

Using the previously described electromagnetic mixers 10, 20, 30, 40, 40 '; 50, 50 '; 60, 60 '; 70, as already mentioned, it is possible to induce in the liquid core of the draft blank preform under the action of electromagnetic induction forces in the region of the shelf sections and / or the transverse section, mixing movements across the casting direction, and thereby the liquid steel in the liquid core of the draft blank is mixed between the shelf sections and transverse section. Due to this, it is possible to actively influence the flow conditions and temperature in molten steel inside the crust of the rough profile and lead to the following effect:

- stabilization of the level of the bath mirror by suppressing turbulence also with changing process parameters such as: casting speed, position of the metal mirror (in order to avoid non-metallic inclusions, as well as gas bubbles in the surface of the cast billet);

- favorable, controlled flow conditions with deliberate mixing between both thickened parts of the inner space of the mold through a thin transverse section, as well as with asymmetric casting and due to this the formation of a uniform thick crust of the workpiece with a favorable solidification structure to avoid shrinkage of shells and / or core porosity;

- avoidance of freezing during solidification despite narrow proportions in the wall of the cross section of the inner space of the mold.

Due to the free choice of connecting the poles to the individual phases of the three-phase current, it is possible to construct various components of the moving field in the liquid core of the draft blank without constructive changes of the mixer, depending on the casting parameters, such as the filling system regarding the pouring place, the number of filling cups, open or closed pouring, speed casting, casting temperature, steel composition, etc., and thereby create various flows of liquid steel. And it is also possible to use the same mixer equipment for crystallizers with different product parameters, such as: dimensions of the rough profile and so on, and at the same time change the connection of the poles so that, depending on the product parameters, rotating and / or transverse sections can be generated in the shelf sections linear mobile fields for the targeted production of liquid steel flows.

The drawings show schematically a shell mold. Instead of a shell mold according to the method of the invention, all mold designs suitable for rough profiles can also function, such as block or plate molds and others, and accordingly, the device of the invention can be used.

Claims (14)

1. The method of continuous casting of steel draft profiles, in particular I-beam draft profiles, comprising the vertical supply of molten steel into the molding space of the mold (1), the cross section of which consists of two shelf sections (2, 3) and one transverse section (4), the effect on the liquid core of the draft blank preform with a magnetic field, the receipt of partially hardened draft blanks in the guide wiring of the secondary cooling device, characterized in that the liquid core of the preform in they are driven by the electromagnetic field created by the coils of the electromagnetic mixer of the three-phase current, while the coils (19) of the mixer are supplied with a three-phase alternating current so that electromagnetic traveling fields with components directed across the movement of the workpiece are generated in the liquid core of the draft blank, and in shelf sections (2 , 3) traveling mold fields with equally or oppositely directed rotating components and / or in the transverse section (4) generate running fields with linearly directed components. 2. The method according to claim 1, characterized in that the traveling fields are generated on the part of the flow mold (1). 3. The method according to claim 1 or 2, characterized in that the traveling fields generate at different height sections of the draft blank. 4. The method according to claim 1, characterized in that in the region of both sections (2, 3) of the shelves, in particular, in the transition zone to the transverse section (4), traveling fields are generated in the liquid core with equally or opposite directions of rotation. 5. The method according to claim 1, characterized in that in the region of the transverse section (4), traveling fields are generated in the liquid core with unidirectional or opposed linear directions. 6. The method according to claim 1, characterized in that the molten steel through the asymmetrically located pouring glass (48) enters the shelf section (2, 3) of the molding space. 7. A device for the continuous casting of steel draft profiles, in particular I-beam draft profiles, containing a mold, the molding space of which consists of two shelf sections (2, 3) and one transverse section (4), and a guide wiring of the secondary cooling device installed behind the mold characterized in that it is equipped with an electromagnetic mixer with six or more poles connected to the phases of the three-phase current so that the magnetic poles of the mixer generate electromagnetic traveling a field with components directed across the movement of the workpiece, moreover, traveling fields with rotating components are generated in the shelf sections (2, 3) and / or traveling fields with linear components are generated in the transverse sections (4). 8. The device according to claim 7, characterized in that the pole pieces (12, 13, 14, 15, 16; 22, 23, 24, 25, 26, 27) are located on one integral yoke. 9. The device according to claim 7, characterized in that the stirrer (10, 20) has a ring-shaped surrounding a flowing crystallizer (1) one-piece yoke (11, 21), along the perimeter of which six pole shoes are unevenly distributed (12, 13, 14, 15, 16, 17; 22, 23, 24, 25, 26, 27) so that they are directed to sections (2, 3) of the shelves and the transverse section (4) or only to the transverse section (4). 10. The device according to claim 7, characterized in that the mixer (30, 70) has a one-piece, external flow-through crystallizer (1) yoke (31, 71) in the form of a rectangular frame, the longitudinal sides of which have three pole pieces (34, 35, 36, 37, 38, 39; 74, 75, 76, 77, 78, 79) located along the width of the mold, and the transverse sides - along one middle pole tip (32, 33; 72, 73), oriented frontally to sections (2, 3) of shelves. 11. The device according to claim 7, characterized in that it is equipped with a second stirrer, with two stirrers (40, 40 ') and, respectively, two yokes (41) 41' divided among themselves on a wide part of the ramjet mold (1), respectively one front end directed at the corresponding section (2, 3) of shelves with the middle pole tip (42, 42 ') and two at both sides of the section (2, 3) of shelves with pole tips (43, 44, 43', 44 ') are located outside the flow mold (one). 12. The device according to claim 7, characterized in that it is equipped with a second stirrer, with two stirrers (50, 50 ') and, respectively, two yokes (51, 51') separated from one another with three pole tips (52, 53, 54 ; 52 ', 53', 54 ') are located outside in the direction of thickness on the flow-through mold (1), and three pole tips are distributed along the width of the mold, and two of them are laterally directed to sections (2, 3) of the shelves, and the middle the pole piece faces the transverse section (4). 13. The device according to claim 7, characterized in that it is equipped with a second stirrer, with two stirrers (60, 60 ') and, respectively, in the direction of the thickness of the mold (1), two yokes (61, 61') separated from each other with three pole tips (62, 63, 64; 62 ', 63', 64 ') are located on the flow mold (1) outside, and these three pole pieces are distributed across the width of the transverse section. 14. The device according to any one of paragraphs.9-11, characterized in that it is equipped with a second mixer, moreover, the mixer (40, 40 '; 50, 50'; 60, 60 ') and, accordingly, the yoke (41, 41'; 51, 51 '; 61, 61') are located on the mold opposite to each other with a displacement in height, and the order of their location in the mold height does not depend on one another.

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